This invention relates to semiautomatic defibrillators, in which an advisory algorithm advises an operator as to whether a shock should be delivered, and it is left to the operator to initiate delivery of the shock.
Semiautomatic defibrillators are well known. They have been in use in one form or another for nearly twenty years. An advisory algorithm analyzes a patient's electrocardiogram (ECG), and gives the operator an advisory indication of whether a shock should be delivered. Typically, the advisory algorithm analyzes the ECG for both ventricular fibrillation and shockable high rate tachycardia. If either is found, the unit will advise the operator that a shock should be delivered. The operator then simply presses a button to deliver the shock. Such units typically have a standby mode used after a patient has been stabilized (e.g., while the patient is being transported to a hospital), in which an alarm will sound indicating that the patient should be checked. The same advisory algorithm, which checks for ventricular fibrillation and shockable tachycardia, is used to trigger the alarm. Following such an alarm, the operator is expected to initiate a further analysis of the ECG, and then to deliver a shock if the advisory algorithm so recommends.
In manual defibrillators, the type of units used by physicians and nurses, and by highly-skilled EMTs, the automated ECG analysis found in semiautomatic units is not provided, and instead the operator is required to makes his or her own decision whether to apply a shock based on a display of the ECG. But it is typical to provide the operator with a heart rate alarm, which is triggered when the QRS detector (essentially a heart rate tachometer) indicates that the heart rate is above or below preset limits. Ordinarily, the heart rate is averaged over several heart beats in order to improve its accuracy. The alarm is useful for signalling an operator of asystole (no heart activity), bradycardia (abnormally slow heart rate), or tachycardia (abnormally high heart rate).
Monitoring equipment of the type used in the cardiac care units (CCUs) of a hospital perform a variety of tests on the ECG, including both heart rate as well as analysis for fibrillation and tachycardia, but these units are for monitoring only, and provide no defibrillation stimuli.
External pacing units have provided heart rate alarms of the same sort as found in manual defibrillators. Such units are typically used by the same skilled practitioners as operate manual defibrillators.